Pete the Invincible is the same guy as Pyro Pete, the boss you had to kill in order to rank up on the Torgue leaderboards. Only this time, he's buffed up and ready to kill the crap out of you.

There is no real trick to defeating this raid boss. Simply shoot him with lots of bullets. DO NOT USE FIRE OR CORROSIVE WEAPONS! Slag him whenever you have the chance and use an electrical weapon to take down his shield.

Pete will immediately drop down and chase after the closest person to him while spraying you with fire. Run away. If you're playing with more than one person, now would be a good time to have one of your mates slag him and work on that shield.

After a few hits on him, Pete will launch a wave of corrosion on everyone. Keep in mind, there is no way to avoid corrosion when he does this. Also, the corrosive damage will deplete your health permanently until you get downed or until you run over to the pipes that have a green lit valve. Turn the valve and it will release water to wash the corrosion off.

Spinning the valve will release a number of Rats and Spiderants. Each time you spin the valve means another wave of enemies. These enemies that spawn actually do more damage than Pete himself as they can be anywhere from five levels lower to thirteen levels higher than you, depending on how much health Pete has left and the amount of times you spin the valves. Work on getting rid of them while still occasionally getting Pete's health down. It's not a race to finish the fight so take your time and make use of the ammo stations around the arena.

Once Pete's health is gone, all other enemies disappear/die so there is no need to worry once Pete is defeated. Pete will fall and drop a sweet amount of loot and Seraph Crystals. Pick up what weapons you find the most interesting and head on back to Mad Moxxi's Bar in the Badass Crater of Badassitude.